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There is a conflict between increasing the image swath and improving the azimuth resolution in a conventional single-channel synthetic aperture radar (SAR) system. This paper introduces a method of...

Two novel series of poly(aryl ether ketone)s (PAEK) bearing pendant carboxylic acid groups have been synthesized, and subsequently sulfonated to obtain sulfonated poly(aryl ether ketone)s with carboxylic acid groups (SPAEK-COOH-x). The expected structures of the sulfonated copolymers were confirmed by FTIR. Modified nanocrystalline cellulose (NCC) was prepared and introduced into the SPAEK-COOH-x as the “performance-enhancing” filler and crosslinking agent. The nanocomposite proton exchange membranes were prepared via a solution-casting procedure. The composite membranes containing NCC presented the higher proton conductivity and better mechanical properties. After further crosslinking, the covalent crosslinked composite membranes showed even better mechanical properties while the proton conductivity and thermal stability were maintained. The hydrophilic/hydrophobic domains were observed from the TEM morphology investigation of COOH-10/NCC-y and C/COOH-10/NCC-y membranes. A balance of mechanical stabilities, proton conductivity, and thermal property could be designed by the incorporation of NCC and the crosslinking between NCC and SPAEK-COOH-10 to meet the requirements for the applications in the fuel cells.

In the presence of range ambiguity, the synthetic aperture radar (SAR) systems suffer from image aliasing, which dramatically degrades the quality of SAR images. In this article, an easy-to-implement technique for range ambiguity suppression is investigated, which is based on phase coding in the transmit pulse dimension, referred to as pulse phase coding (PPC). By properly designing the PPC series, it is possible to discriminate the range ambiguous echoes from different range areas in the Doppler frequency domain. To further suppress the range ambiguous echo, a two-pulse cancellation (TPC)-based SAR imaging method is proposed, which improves the quality of SAR images in the presence of range ambiguity. The proposed two-pulse cancellation is performed followed by the azimuth compression. The simulation results demonstrate the effectiveness of the proposed method.

Space-time coding radar has been recently proposed and investigated. It is a radar framework which can perform transmit beamforming at the receiver. However, the range resolution decreases when the number of the transmit element increases. A subarray-based space-time coding (sub-STC) radar is explored to alleviate the range resolution reduction. For the proposed radar configuration, an identical waveform is transmitted and it introduces a small time offset in different subarrays. The multidimensional ambiguity function of sub-STC radar is defined by considering resolutions in multiple domains including the range, Doppler, angle and probing direction. Analyses on properties of the multi-dimensional ambiguity function of the sub-STC radar with regard to the spatial coverage, resolution performance and low sidelobes are also given. Results reveal that the range resolution and low sidelobes performance are improved with the proposed approach.